Ricky444 Posted February 1, 2020 Share Posted February 1, 2020 Hi Folks currently run a 3.14 in my hayabusa sprints/Hillclimb car would it be a great benefit to change the ratio to a 3.38. Thanks in Advance Richard Quote Link to comment Share on other sites More sharing options...
stephenh Posted February 1, 2020 Share Posted February 1, 2020 What is your top gear ratio, and what size rear tyres? What gear and revs do you pull on the fastest straight you get on on the tracks you visit? Or is this for future competition? Personally, when I was sprinting, the fastest I went was on the railway straight at Aintree (depending on the wind direction, which could make a big difference to something like a Westfield at those speeds) so I wanted gearing which meant that at that circuit I was pulling a bit less than max. revs in top as I hit the finishing line on that straight, given a following wind, the rev point at which I was getting max. power from my engine. From that, I worked backwards using maths to work out what diff. ratio I needed. Quote Link to comment Share on other sites More sharing options...
K17 CAR Posted February 1, 2020 Share Posted February 1, 2020 I run a 3.21 wish I had the option of a 3.14, I bounce off limiter in top at Cadwell & Snetterton and that's with a longer 5th & 6th gear, I hit limiter at Snetterton even if I put 15" wheels on rear. 13" wheels? Don't change it. Quote Link to comment Share on other sites More sharing options...
Ricky444 Posted February 1, 2020 Author Share Posted February 1, 2020 Cheers I run 13 inch Toyos Quote Link to comment Share on other sites More sharing options...
Kingster Posted February 1, 2020 Share Posted February 1, 2020 10 minutes ago, Ricky444 said: Cheers I run 13 inch Toyos In fairness that’s not as lot of help 😁 You need to add which size (width and aspect) as that has a rather big effect on diameter 👍 1 Quote Link to comment Share on other sites More sharing options...
Ricky444 Posted February 2, 2020 Author Share Posted February 2, 2020 205/60/13 Toyo I always lose 0.1 to 0.2 on the 64ft line but have won both championships in Northern Ireland last year Quote Link to comment Share on other sites More sharing options...
K17 CAR Posted February 2, 2020 Share Posted February 2, 2020 Have a look on Avons Motorsport tyres page, there's a good list on there that gives diameter and revolutions of wheel per mile on all trye sizes, in 13" over the rim widths we tend to use there's not a huge difference in diameter/revolutions per mile. Do you get near limiter in 6th on any of the circuits you run on? Quote Link to comment Share on other sites More sharing options...
S2T Posted February 2, 2020 Share Posted February 2, 2020 Top Speed 3.14 diff 136mph (theoretical) with 13" 60 profile tyres, 126mph with 3.38. Acceleration would be better with a 3.38. So in theory 3.38 better for the hills and 3.14 better for sprints especially those with long straights Quote Link to comment Share on other sites More sharing options...
Ricky444 Posted February 2, 2020 Author Share Posted February 2, 2020 Thank you folks I think I will just stay with the 3.14 Quote Link to comment Share on other sites More sharing options...
cast iron Posted February 3, 2020 Share Posted February 3, 2020 I ran a 3.14 albeit with a standard fire blade, similarly running 13" wheels. I couldn't get out of 4th gear! I run a 3.63 now and hit the limiter in 6th just braking for stowe at Silverstone seeing 125MPH according to their speed trap I think your better off having the acceleration out of the corners over top speed, you always use acceleration! Quote Link to comment Share on other sites More sharing options...
Terry Everall Posted February 20, 2020 Share Posted February 20, 2020 Remember that the gears on a Busa are different to a Fireblade. On my 1300, 1400 and 1548 Busa I always ran the 3.14 with no problems of acceleration or topped so I would stick with the 3.14 Quote Link to comment Share on other sites More sharing options...
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